1. Field of the Invention
This invention generally relates to a ship, and more particularly to a ship having a bilge area located within the hull adjacent the bottom thereof. Such a bilge area can typically be located at a lowest point within the hull and therefore can be used as a collection site for water which may leak into the hull, Such water then generally needs to be transported from bilge to insure that equipment, etc, located in chambers above the bilge does not get wet.
2. Background Information
In a typical ship construction, the ship will have an outer hull which is generally water-tight, along with what could be termed an inner hull that defines the interior dimensions of the ship, that is, the walls and floors of the various compartments which make up the interior of the ship. An inner hull can also serve as a second means for protecting the ship from taking on water if the outer hull should be ruptured, such as during a collision, etc. The compartments within the ship can essentially comprise several holds for storage of goods, as well as machinery rooms, such as the engine room wherein the ships engines are located.
Because a ship will more than likely take on some water, either because of small leaks in the hull, rainstorms, or even large waves which may wash up on board, the interior space of the ship, such as a space between the ship's inner and outer hulls, can typically be designed to include a bilge area for collecting the undesired water. In order to protect the equipment, etc. from getting wet should the water level increase to an undesirable level, the bilge area can also be outfitted with pump devices which can pump the water out of the bilge. It is generally desirable to pump this water from the bilge off of the ship, as space on board is typically limited, and storage space for water would prohibit the ships space from being used for transporting cargo, etc. However, because of all of the machinery on board, there is also a good possibility that at least some oil, or other substances used on board will leak into the water drainage system, thus contaminating the water and making the water generally environmentally unsafe to pump directly back overboard, without first treating the water to remove the contaminants therefrom. In addition, the water and oil mixture can also be emulsified, that is, the oil can be distributed as fine droplets throughout the water, thereby making separation even more difficult. Therefor, a ship will generally need to be outfitted with some type of separating apparatus for cleaning the water. The type of separation for cleaning the water can essentially be based on a gravity separation of the oil from the water.
It is well known that bilge water contaminated with oil cannot be pumped overboard without first having been treated to remove the contaminants therefrom. That is, the bilge water must typically first be cleaned before it is dumped, so that the contaminants therein do not pollute the environment, i.e., the ocean, or a canal system if the vessel is operating on inland waterways. However, there are many difficulties with known cleaning methods, because the oil cannot be easily separated to the desired degree using gravity separation as the principle separation step. The primary reason for this problem is that bilge water tends to contain chemical components consisting of cleaning agents, additives from the engine coolant and anti-corrosion agents, which components can promote the formation of an emulsion consisting of water and oil, and thus further complicate separation of the oil from the water.
Methods currently used to clean oily bilge water by gravity separation are complex and expensive, and the known methods are generally still unsatisfactory because they leave an excessive amount of oil in the allegedly clean water.